I'm driving from Vancouver, BC to Salt Lake City and plan to take most direct route.
I-90 to Seattle then I-82 to Yakima & Richland, Pendelton, Oregon then I-84 thru NE corner of Oregon, staying on I-84 thru Idaho and Utah. Any idea how long this drive will take or the travel thru the mountains in Washington? Is this the most direct route?
Any ideas would be appreciated.

You are looking at slightly more than 1000 miles of Interstate driving.
The major stumbling block will be Seattle. I am sure you are well aware that traffic in that delightful city can be slow at times, particularly during the morning and evening traffic peaks.
I don't think the mountains will hold you up much, unless you are driving a heavy rig that has trouble going up the grades. (I am assuming that you are not going until later in the year and that snow at the higher elevations is a non issue.)
A 1,000 miles is a little more than I normally drive in a day. So if you stop to spend the night at about the 550 mile mark you will have about an equal drive the following day.
Once east of the Cascades, you should have no trouble averaging 70 mph plus while you are driving. In fact, the last time I drove in Idaho, I found that 75 mph at times was holding up traffic.
Have fun.

Thanks for the input Bob. I'm travelling April 15th so am worried about snow etc. I will be travelling thru Seattle on Sunday so don't think the traffic will be a problem. I am a 52 year old woman driving alone, I do have a new 4 wheel drive SUV so should have no mechanical worries, just unsure about the weather and roads thru the Cascades.
I live on Vancouver Island, so plan on taking the ferry over after work on Saturday night, should reach the mainland about 8PM at Tsawwassen then travel to the border and drive as far south as I can before I fall asleep! I should be thru Seattle early Sunday morning then have a good day to get thru the Cascades

I find driving on the Interstates boring . If you have a CD or tape player take along something to keep you awake.
I have not driven long distances alone in a long time, but coffee and cokes were necessary to keep alert.
I would not drive the first day until I was done in. And stop to get out of the car every two hours or so to keep from getting totally road happy.
The only suggestion I have for the weather is to keep an eye on the weather channel!

Good idea for CDs or tapes--think about "books on tapes" I find they are entertaining and do not lull you into relaxed state like some musical selections When I travel alone I seldom try to cover more than 400-500 miles. I am 50+ have gone solo many times. One of my main goals is to be on the road ONLY in daylight hours, have a cell phone and emergency road service..
Be sure you turn off Interstate 5 to the 405 to get to I 90. You'll have great trip..

Laurie, it will be extremely unlikely that driving conditions crossing the Cascades (I-90) will be hazardous in mid April. Seattle to SLC should be around 13-14 hours depending on your foot and frequency of stops; add 3 additional hours or so from Vancouver. After the Cascades, though, it's not the most visually inspiring journey, so boredom might become a factor.
It is probably the most direct route in terms of time, given that it's freeway the entire route, as opposed to going east on the TC Hwy, then south or southeast over to I-15 in Montana, thence south, or some other route on non-freeway US routes. Get an early start so you can get to the US border queue at Blaine before it gets awful.